Demountable heat sink

ABSTRACT

A demountable, and thus re-usable, conductive heat sink for dissipation of excess heat of an electronic component. The heat sink uses a T-bolt and T-slot for attachment to the electronic component and the printed circuit board, respectively. This attachment eliminates the typical concerns associated with the placement of traces on the PCB to accommodate the holes placed therein for the attachment of conventional heat sinks. The improved designed also facilitates demounting of the heat sink from the printed circuit board and the electronic component without damage thereto.

This application is a continuation of Ser. No. 08/583,322 filed Jan. 1,1996.

BACKGROUND

1. Field of the Present Invention

The present invention generally relates to heat sinks, and morespecifically, to demountable conducting heat sinks for electroniccomponents containing semiconductor devices.

2. History of Related Art

In today's modern electronic industry, many of the electronic componentsgenerate excess heat which must be dissipated in some fashion. Thedissipation of this excess heat is, typically, accomplished by attachinga heat sink to the electronic component. Heat sinks, which arerelatively small in size, use some type of thermal adhesive for theirattachment to the electronic component. Heat sinks, which are relativelylarge in size, use a demountable scheme having a thermal compoundlocated between the heat sink and the electronic component. A typicaldemountable scheme may use, for example, a nut and bolt, or clip.Unfortunately, the types of demountable heat sinks currently used by theindustry have several problems associated with them. First, it is wellunderstood by those of ordinary skill in the art that whenever anelectronic component is assembled using a solder column or solder ballattachment to a Printed Circuit Board (PCB), a good thermal interfacebetween the heat sink and the electronic component must be established.This is usually accomplished by applying force to the connection therebetween via a nut and bolt or clip. When excessive force is used inestablishing the interface, damage to the solder ball or column may beoccur. Secondly, many of the currently used heat sinks require thedrilling of holes through the PCB in order to accommodate the nut andbolt attachment mechanism. This procedure unnecessarily complicates therouting of the various traces on the PCB, and in some cases, may resultin a less desirable design. Thirdly, the methods currently used fordemounting the heat sink, which has been attached to the electroniccomponent using an adhesive, often results in damage to the heat sink,electronic component, and/or PCB.

It would, therefore, be a distinct advantage to have a demountable heatsink that would eliminate the concern of applying excessive force inestablishing the interface between the heat sink and the electroniccomponent, which would attach to the PCB without requiring the drillingof holes for the attachment, and which would be removable, and thereforere-usable, without damage to the heat sink, PCB, and/or electroniccomponent.

SUMMARY OF THE PRESENT INVENTION

In one aspect the present invention is a heat sink for dissipatingexcess heat from an electronic component mounted to a printed circuitboard. The heat sink includes fastening means having an upper and lowerattachment means. The heat sink further includes retaining means,attached to the surface of the printed circuit board, for receiving andretaining the lower attachment means. The heat sink also includes heatdissipation means for dissipating excess heat from the electroniccomponent. The heat dissipation means having receiving means forreceiving the upper attachment means. The heat sink further includingsecuring means for securing the upper attachment means to the heat sink.

In yet another aspect, the present invention is a method of attaching aheat sink to an electronic component mounted to a printed circuit board.The method includes the steps of attaching the electronic component tothe printed circuit board, and attaching retaining means, for receivingand retaining a lower attachment means, to the surface of the printedcircuit board. The method further includes the steps of inserting lowerattachment means of a fastening means into the retaining means, andinserting upper attachment means of the fastening means into a receivingmeans of the heat sink. The method also includes the step of securingthe fastening means to the heat sink with securing means, therebyattaching the heat sink to the electronic component and the printedcircuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood and its numerous objectsand advantages will become more apparent to those skilled in the art byreference to the following drawings, in conjunction with theaccompanying specification, in which:

FIG. 1 is a diagram of a heat sink and two electronic componentsaccording to the teachings of the present invention;

FIG. 2 is a diagram illustrating the heat sink attached to theelectronic component of FIG. 1 and a printed circuit board according tothe teachings of the present invention; and

FIG. 3 is a flow chart comprising a method of attaching the heat sink ofFIG. 1 to the electronic component and the printed circuit board of FIG.2 according to the teachings of the present invention; and

FIG. 4 is a flow chart comprising a method of demounting the heat sinkfrom the electronic component and printed circuit board of FIG. 2according to the teachings of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE PRESENTINVENTION

Reference now being made to FIG. 1, a heat sink 102 and two electroniccomponents 106 and 104 are shown according to the teachings of thepresent invention. Heat sink 102 includes four circular holes or othershaped holes (e.g.slots), two of which are shown and designated as 102aand 102b. The two electronic components 104 and 106 are illustrated asbeing attachable to a Printed Circuit Board (PCB), via a solder ball106a or solder column 104a, respectively.

Reference now being made to FIG. 2, heat sink 102 is illustrated asbeing attached to the electronic component 106 of FIG. 1 and a printedcircuit board 202 according to the teachings of the present invention.Although the heat sink 102 is shown as already being attached toelectronic component 106 in FIG. 1 and PCB 202, it is beneficial, atthis point, to discuss the method for the attachment of the heat sink102 thereto.

Reference now being made to FIG. 3, a flow chart is shown illustratingthe method comprising the attachment of the heat sink 102 to theelectronic component 106 and the PCB 202 of FIG. 2 according to theteachings of the present invention. The method begins at step 300 andproceeds to step 302 where the PCB 202 and the electronic component 106are prepared for normal surface mount assembly. The methods used for theabove preparation are well known and understood by those of ordinaryskill in the art, and therefore, further discussion of the methods aredeemed unnecessary. After the electronic component 106 and the PCB 202have been prepared for surface mount, the method then proceeds to step304 where the T-slot 204 is attached to the PCB 202. The method thenproceeds to step 306 where the T-bolt 212 is placed in the T-slot 204.Thereafter, the method proceeds to step 308 where the spring 220 isplaced on the T-bolt 212.

In an alternative embodiment, the spring 220 can be pre-attached to theT-bolt 212, thereby, eliminating the above step 308. The method thenproceeds to step 310 where a thermal compound, such as thermal grease isapplied to the surface of the electronic component 106 to which the heatsink 102 is to be attached. As shown in FIG. 2, the heat sink 102 isattached to the top portion of the electronic component 106 via thermalcompound 218. Thereafter, the method proceeds to step 312 where the heatsink 102 is placed on top of the electronic component 106 so that theT-bolt 102 protrudes through the cylindrical or other shape hole 102a. Apre-load nut 206, a lock washer 208, and lock nut 210 are then placed ontop of the T-bolt 202 to secure the heat sink 102, the electroniccomponent 106, and the PCB 202. The method then proceeds to end at 314.It should also be noted that the number of T-slots used in order toproperly mount the heat sink 102 to the PCB 202 is dependent upon theheat sink size, total force, and uniformity of pressure for theparticular design.

Reference now being made to FIG. 4, a flow chart is shown comprising themethod of demounting the heat sink 102 from the electronic component 106and PCB 202 of FIG. 2 according to the teachings of the presentinvention. The method begins at step 400 and proceeds to step 402 wherethe lock nut 210, the lock washer 208 and the preload nut 206 areremoved from the T-bolt 212. The method then proceeds to step 404 wherethe heat sink 102 is removed from the electronic component 106.Thereafter, the method proceeds to step 406 where the spring 220 isremoved from the T-bolt 212. The method then proceeds to step 408 wherethe T-bolt 212 is removed from the T-slot 204, and the method proceedsto end at step 410.

The above removal of the heat sink 102 provides the ability to repairand/or remove a defective electronic component 106. Thus, providing anefficient and effective method for re-use of the demountable heat sink102. In the preferred embodiment of the present invention, a T-bolt 212and T-slot 204 have been used to attach the heat sink 102 to theelectronic component 106 and PCB 202. The selection of the T-shapedmembers (T-bolt 212 and T-slot 204) is preferable to other equivalentshapes as a result of cost and manufacturing perspectives, as well asthe attachment and demounting of the heat sink 102. It should be clearlyunderstood, however, that the scope of the present invention, is notintended to be in any way limited to the use of such T-shaped members,but in fact, may use any shape members. (e.g. square, semi-circle,triangle, or bolt threaded at two ends (functioning as T-bolt), andthreaded flange nut (functioning as T-slot)) which essentiallyaccomplish the same purpose of the T-shaped members.

It is thus believed that the operation and construction of the presentinvention will be apparent from the foregoing description. While themethod and system shown and described has been characterized as beingpreferred, it will be readily apparent that various changes and/ormodifications could be made wherein without departing from the spiritand scope of the present invention as defined in the following claims.

What is claimed is:
 1. An apparatus comprising:a printed circuit board;an integrated circuit attached to a surface of said printed circuitboard; a heat sink placed on top of the integrated circuit; a bolthaving upper and lower portions; a non-threaded slot having the sameshape as the upper portion for receiving the upper portion andrestraining the upper portion from vertical movement, the non-threadedslot being attached to the surface of the printed circuit board; aspring located between the bottom of the heat sink and the top of thenon-threaded slot; and securing means for securing the lower portion tothe heat sink and for applying an upward force via the spring to theupper portion such that the upper portion is restrained from horizontalmovement via the non-threaded slot.
 2. The apparatus of claim 1 whereinthe non-thread slot is substantially similar in length to that of theheat sink.
 3. The apparatus of claim 2 wherein the upper and lowerportions of the bolt are a threaded end and a T shaped end,respectively.
 4. The apparatus of claim 3 wherein the non-threaded slotis T shaped.
 5. The apparatus of claim 1 wherein the upper and lowerportions of the bolt are a threaded end and a T shaped end,respectively.
 6. The apparatus of claim 5 wherein the non-threaded slotis T shaped.